Add Doxygen documentation for API changes from 1.6.0 to 1.6.1

Copied from my review board description:
This is a continuation of the API changes documentation started for describing
changes between releases. Most of the API changes were pretty simple needing
only to be brought to attention via the new "Asterisk API Changes" list.
However, if you see anything that needs further explanation feel free to
supplement what is there. The current method of documenting is to add (in the
header file): \version <ver number> <description of changes> and then to add
the function to the change list in doxyref.h on the AstAPIChanges page. I also
made sure all the functions that were newly added were tagged with \since
1.6.1. I think this is a good habit to start both for the historical aspect as
well as for the future ability to easily add a "New Asterisk API" page.

Review: http://reviewboard.digium.com/r/190/


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@180719 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/enum.c

@@ -915,14 +915,6 @@ int ast_get_enum(struct ast_channel *chan, const char *number, char *dst, int ds
 	return ret;
 }
 
-/*!\brief Get TXT record from DNS.
- * Really has nothing to do with enum, but anyway...
- *
- * Actually, there is now an internet-draft which describes how callerID should
- * be stored in ENUM domains: draft-ietf-enum-cnam-04.txt
- *
- * The algorithm implemented here will thus be obsolete soon.
- */
 int ast_get_txt(struct ast_channel *chan, const char *number, char *txt, int txtlen, char *suffix)
 {
 	struct txt_context context;